The invention concerns a short-circuit protected mains supply unit that can be electronically switched on at a control terminal. A mains supply unit of this type is needed in the television-screen text component of a television receiver for example. Electronic switching is necessary because the mains supply unit is intended to be switched on from the remote-control unit only during television-screen text operation.
The longitudinal path of known stabilized mains supply units generally contains a transistor, and the base of the transistor is controlled to stabilize the output voltage. The collector of another transistor is connected to the base. A reference voltage from a Zener diode is applied to the emitter of the second transistor and a controlled stabilization variable in the form of part of the output voltage is applied to its base.